Platinum Metals Review - Volume 43, Issue 1, 1999

Platinum metals, particularly platinum and palladium, are used extensively in low resistance, relatively stable and laterally uniform ohmic contacts made to semiconductor devices formed from Group III and V elements. Palladium is primarily utilised as one component of a multilayer metallisation structure, improving adhesion to the semiconductor, while platinum is commonly used as a diffusion barrier to minimise interdiffusion between metal and semiconductor components. This paper describes the roles of platinum and palladium in ohmic contacts, gives examples of their typical utilisation and outlines the design considerations associated with the formation of reliable ohmic contacts.

There is a constantly increasing need for metallic materials with melting points over 1700°C for use at very high temperatures. In contrast to the refractory metals: tantalum, niobium, tungsten, molybdenum and rhenium, which also have very high melting points, the metals of the platinum group, particularly platinum, rhodium and iridium, are characterised by outstanding chemical stability, oxidation resistance and resistance to many molten oxides. The platinum group metals are therefore ideal materials for using at high temperatures while undergoing simultaneous chemical attack and mechanical loading. However, for optimum effective employment of these metals, it is necessary to know their strength and deformation behaviour at extremely high temperatures. Data have therefore been collected from comparative investigations of platinum, platinum alloys, dispersion hardened platinum materials, rhodium and iridium, and the compilations are presented here.

The founding of a platina refinery in Madrid in 1786 required the establishment of a system for collecting platina from the Chocó district of New Granada in South America and shipping it to Spain. After several unsuccessful attempts to amass platina over many years, the Viceroy of New Granada ordered a district attorney at the Santa Fé Audiencia to arrange an official visit to the Chocó district to establish a Royal monopoly in platina and to set up a local collection procedure. This time it was successful and the shipment to Spain of a considerable amount of platina took place between 1788 and 1805.